Publisher/Editor: ». D. Cheek. Sr. aka "Dr. Sigorjort is" V1W9: October. 1991
THE WORLD SCANNER REPORT
4 Journal of VHF-UHF Scanner Technology i Engineering
iblished at: COhHtronics Engineering; PO BOX 262478; San Diego. CA 92196 Copyright (c) 1991 <Al 1 Rights Reserved) iUI
TECHNOLOGY SPINS OFF FOR YOU!
It's an interesting daydream that if the typical 1942
mi 1 itary monitoring post were equipped comparable to
today’s typical hobby monitoring post, that WW-II might
have been won in half the time! We'll never know for
sure but it's an interesting whimsy, huh? We do know
however, that today's typical hobby monitoring post is a
spinoff of NASA and Viet Nam technology. The results of
research & development for space and defense programs
continues to filter down to the consumer level. While
this may be difficult for the casual hobbyist to fully
comprehend, I am pleased to offer you this month a small
scale spinoff that can be understood. Let me explain —
As you probably know, my keenest focus in scanners has
been on the Realistic PRO-2004/5/6 series. I doubt if
this has caused any wholesale problem since over half the
readers of the WSR own one of this series. But what
about those who don’t? That is where the spinoff comes
into focus. Two examples come to mind: one, the Generic
S-Meter for all scanners & other radios that appeared in
V1N7 of the WSR. It was rather easy to adapt an S-meter
to the PRO-2004/5/6, but unheard of for other scanners.
1 1 most intnediately after Vol-1 of my SCANNER MOO HANDBOOK
was published, I was beseiged with requests for an
S-Meter for other scanners so I set about to learn all
there was to know about S-metering. Where there's a
will, there’s a way and the universal S-Meter was the
result. Now there's another spinoff for you this month.
One of the first modifications I performed to my PRO-2004
back in late 1986 was to incease the speed of the SCAN &
SEARCH modes with a 10 MHz quartz crystal in place of the
stock 7.37 MHz resonator. Fine and dandy, but the DELAY
function got shortened by 35$ thereby highlighting a need
for an Extended Delay function. Mark Persson of New York
admirably responded with MOD-29 for Vol-2 of my book. But
this left me with a familiar problem: the Extended Delay
for the PRO-2004/5/6 didn't work for other scanners, so I
burned the midnight oil to develop an alternate Extended
Delay. The method that I selected for page 157 in Vol-2
of my book worked well enough, but it was cumbersome and
with three chips, was a bit too large for most handheld
scanners. On top of that, some readers had problems
adapting that circuit to various scanners. Spinoff time:
I just KNEW there had to be an easier & better method of
Extended Delay for scanners other than the PRO-2004/5/6.
There was and it's here for you this month. The original
MOD-29 method for the PRO-2004/5/6 remains unchanged but
for other scanners, we've got one just as easy now! Make
two small wiring changes to MOD-29 in my book and you've
got an Adjustable Extended Delay (MOD-29b) that will work
for most any other scanner in which MOD-29 doesn't work!
FRONT END TRANSISTOR FAILURE IN THE SONY ICF-2010
(And What You Can Do About It!) by Bob Scott. VA
The Sony ICF-2010 is a popular, potent, and low cost
shortwave receiver. When used with the supplied whip
antenna (or a short indoor wire) it proves to be a
reliable performer with little or no maintenance.
Some hobbyists have extended the reception range of the
ICF-2010 by connecting outdoor long wire antennas or
externally mounted amplified antennas. Although this
makes a remarkable improvement in performance, it can
also lead to the destruction of a fragile Field Effect
Transistor (FET) in the set's radio frequency (RF) front
end. This article will show you how to prevent such
damage and how to recognize and repair a typical failure.
The 2010 uses a 2SK152-1 N-channel FET as a high-gain RF
preamplifier for the internal whip antenna. This FET,
designated Q-303, boosts the feeble signal from the whip
antenna to a proper level for further processing by the
mixer & IF amplifier stages. Connection of an external
antenna to the "AM” antenna input jack bypasses the FET
amplifier. This bypass and lower overall gain prevents
overload of the RF front end from very strong signals
that can enter from a long wire or dipole antenna.
Even when Q-303 is not used for amplification, it's still
in the signal path in an ''idle” mode. When an external
antenna is connected, Q-303 still "sees” the input; it
just doesn't amplify it. Therein lies the problem.
Normally such a sensitive transistor must be shielded
from overloads or static buildup by some type of
protective circuitry. Q-303 is so protected, but only
when it is connected to the internal whip. In that case,
back-to-back diodes protect Q-303 from voltage surges
above three volts. There is no such safeguard for the
external antenna jack.
So, Q-303 will happily self-destruct in the face of high
voltages coming in via the external antenna. Typical
sources of such hazards are nearby powerful transmitters,
close lightning strikes, or static build up in heavy snow
storms. (The latter gremlin terminated my Q-303!)
The answer to this problem takes two forms: protection
and caution. First, exercise caution by disconnecting
the external antenna when the radio is not in use. Your
radio spends most of its time turned off anyway. Simply
disconnecting the antenna during this time is the most
effective protection from static damage. Second, add
some electronic protection. The simplest is to duplicate
the protection circuitry of the telescoping antenna
circuit. Connect two pair of series connected 1N914 or
1N4148 diodes (R/S #276-1620 or 276-1122) in a back-to-
back, reverse polarity as shown in Fig-1. Install the
circuit across your external antenna terminals. The
diodes shunt voltages higher than 1.2v to ground. Normal
RF voltages will not be affected. The diodes are tiny
and will easily fit in the gray junction box supplied by
Sony for connecting an external antenna. Connect the
"Antenna” lead of the diodes to the center conductor
screw in the connector box and the "Ground" lead to the
large metal ground pad below the screw. Use "creative
wire bending"; close the box and secure its cover.
Recognizing a Failure
Since Q-303 is bypassed with an external antenna, failure
can go unnoticed in the SW bands. The first clue might
be a sharp drop in sensitivity on the AM broadcast band,
both with and without the external antenna. The ICF-2010
schematic reveals the reason: when Q-303 fails, typically
a Source-Drain short, the bias voltage to Q-301, (MW/LW
preamp), is shorted to ground. This preamp is used full
time, so a malfunction becomes painfully apparent.
If you suspect Q-303 has blown, disconnect any external
antenna and tune in an AM broadcast signal. Stations
that normally gave a ”10" on the S-meter will be at a 4
or 5. Comparison to a known good radio can confirm poor
sensitivity throughout the range of the 2010, but the
problem will be most apparent in the MW/LW bands. The
best test is the voltage check described below. If you
aren’t comfortable with electronic test equipment, a
technician or a knowledgeable friend can do it for you.
Checking Q-303's operating voltages is the best bet.
Required are an accurate voltmeter (50k-ohms/volt or
better; preferably digital) and a phillips screwdriver.
1. Write down any memory presets you may have programmed.
The memory batteries (2 AA cells) needn't be removed but
they may get jostled and cause a memory loss.
2. Disconnect external devices (AC adapter, tape deck,
etc.); move the 2010 to a comfortable work table.
3. Place the radio face down on a towel, or similar pad,
to protect the face place. Orient the radio with the
battery compartment closest to you and the tuning knob to
your left. Remove the three ”D” cell batteries, if
installed. The two "AA" memory batteries can remain.
4. Touch a grounded object to discharge body static. At
least touch the metal earphone jack on the radio before
proceeding. Avoid static building activities from here
on; shuffling feet on carpet, etc.
5. Remove the seven screws securing the case back. Four
are plainly visible. Two screws are hidden by the rod
antenna, if it is in its stowed position. The last screw
is in the battery compartment. An open arrowhead symbol
clearly marks each screw location. See Fig-4.
6. Carefully lift away the rear case. There are no wires
from the case to the main chassis to get in the way.
7. Behold the wonders of Japanese engineering! Good for
us that Q-303 does not reside on the large main analog
board, but instead on the smaller Jack Board which is the
narrow board to the right of the speaker. See Figs-2 & 4.
8. Use Fig-2 and locate Q-303. Note the meanings of its
three terminals: S-Source, D-Drain & G-Gate. Note that
only the Gate is labeled with a white "G" on the circuit
board. The other two connection pads form a vertical
line up from the "G” lead and are enclosed by a printed
white box. The middle lead is the Source and the upper
one is the Drain. See Fig-3.
3. Connect the AC adapter. Turn on the radio and set it
to AM NARROW mode.
10. Connect the negative lead of your voltmeter to a
chassis ground of the radio. The brown wire soldered
from the metal shield at the top center of the radio to
the center of the main PC board is a good spot.
11. Measure each terminal of Q-303 and compare a
readings with those shown in Table 1. If any are off — oy
more than 105S-20K, you may have a problem. (Measurements
of my Q-303 were grossly off after Q-303 had blown).
TABLE 1: Q-303 OPERATING VOLTAGES
Set Mode to: AM Narrow, Sync OFF
Gate: 0.0 volts
Source: 0.2 volts
Drain: 2.9 volts
12. If the voltages are in spec, or if you don’t wish to
proceed with replacing Q-303 yourself, turn off the
radio, disconnect the AC adapter and restore the case.
Fortune shines again. Most of the 2010 uses hard-to-find
(and replace) surface mount components. Q-303 is a JFET
mounted in a normal through-board style. Replacement is
fairly straight forward, as both sides of the jack board
are easily accessible. You'll need your favorite solder
remover (vacuum or wick), side cutters and a f ine-tip,n^,
low wattage soldering pencil. A new transistor may^i
ordered from your friendly Sony service center as part
number 8-729-800-42. If you don't want to wait for the
next boat from Tokyo, a common 2N3819 works as well as
the Sony part. Radio Shack Catalog #276-2035. Handle
"THE WORLD SCANNER REPORT ' (c) 1991; V1N9 - October, 1991; Page 2
the replacement with care as it is somewhat sensitive to
static discharge (if it wasn’t, you wouldn't need this
article!) To replace the transistor, follow the steps
above for disassembly and then proceed as follows:
difference, try touching an external antenna (or the tip
of its connecting plug) to the collapsed whip. You will
notice a marked signal strength increase compared to
plugging the same antenna into the AM jack.
3. Carefully remove the jack board by tipping up the
edge closest to the speaker about one half inch, then
slide it to the left until it's free of the mounting
posts. No screws secure the board. Be careful of the
fine wires connecting the jack board to the loop antenna.
They are fragile and easily broken if strained.
H. With a helper supporting the board, desolder and
remove <3-303. Note its orientation. You may wish to
clip the transistor body free of its leads first, then
remove each lead individually. Clean out each lead hole
in preparation for mounting the new transistor.
15. If installing the Sony part (or an exact substitute),
just orient the transistor in the same way as the
original and solder in it. Some generic replacements
(such as the Radio Shack 2N3819) may have different lead
arrangements so check the data sheet for your specific
FET . In my case the 3819 had its gate and source
interchanged as compared to the Sony FET. If you are
using a non-Sony replacement transistor and have to cross
leads to fit it properly, slip a small piece of
insulation (from some 22 gauge hook-up wire) over one of
them to prevent a short. Remember, the pads for Q-303
are arranged Gate, Source and Drain from the bottom to
the top of the jack board. Check your FET and do
whatever you must to connect it right!
16. Reinstall the jack board by reversing the procedures
in Step 13. Make sure the switches and jacks line up
properly in their respective holes. Check the AM ATT and
MAIN POWER switches for proper operation.
17. Test out your work by tuning in the AM broadcast
station you used earlier. You should see quite a
difference on the signal strength meter.
18. Replace the rear case and reinstall the batteries.
That’s all there is to it. Using the protective measures
outlined in this article, my replacement transistor has
survived two years of heavy operation. Unless you have
your antenna lead tied off to the lightning rod, there's
no reason you shouldn't have the same results.
If you're interested in doing any serious hacking of the
Sony I CF-20 10 , the Service Manual is a wealth of great
information. It's available from most Sony service
centers as part number 9-951-647-11. Price when I
purchased mine was about $20 and it's well worth every
penny. Now, anybody for a computer control interface?
ICF 2010 Portable Operation Tip
There are drawbacks to the automatic switching of the RF
JFET preamp; i.e., connection of a short external wire is
handicapped by the lack of amplification. To see the
If your external antenna is relatively long, you may hear
several stations at once; the result of RF overload where
strong shortwave or medium wave stations appear at the
multiple false locations in the SW band and obliterate
any weaker signals that lie near them. This is a reason
why amplification is intentionally limited at the input
for an external antenna.
When using short or improvised antennas with the 2010,
try first connecting it to the whip. You'll enjoy a
"free’’ preamplifier. If you notice image problems,
switch to the antenna jack. -Bob Scott-
. £* r ^
V1N9 - October, 1991; Page 3
"THE WORLD SCANNER REPORT* (c) 1991 ;
* * ADVANCE PRCOUCT INFORMATION * *
PRO-2004/5/6 TWO-WAY PC- INTERFACE
B. Bond, Pres.
As you read this issue of the "HSR", HB-Technologies is
vigorously pursuing Phase III of a project to fully
two-way interface the PRO-2004/5/6 to a PC/clone personal
computer. Yes, Phase III implies that previous events
have taken place, and these events are detailed below
exclusively for the readers of the WSR.
Most of you are aware that the PRO-2004/5/6 lack hardware
& software to communicate with a PC. Entrepreneurs have
had limited success with keyboard emulator interfaces to
program the scanner but methods to retrieve, display and
store scanner information remain elusive. Progress is now
being made on developing BOTH SIDES of an interface and
code to perfect this desirable modification. This article
summarizes the work done so far.
PHASE I began with a detailed examination of the existing
hardware within the scanner chassis. P35 (TxD) of the
CPU is a serial pin used in conjunction with P36 (CLK) to
synchronously transfer data to the LCD Display Decoder
and the PLL. Tests revealed an average transfer rate in
excess of 52 Kbaud! Since both LCD and PLL data come out
of the CPU TxD port, we knew that a means had to be found
to distinguish between the two data. Mystique pervaded
Phase I when the LCD data was found to be composed of
command and display bytes. A data analyzer was designed,
prototyped, and built specifically for the purpose of
trapping data relevant ONLY to the LCD Display.
PHASE II sampled the data transfer between the CPU and
LCD Display Decoder. Thousands of bytes were intercepted
and transposed for analysis. In turn, each byte was
tediously correlated to 1 of 151 possible commands and 1
of 100 display bytes. We found that the transfer of data
to the LCD Display Decoder involves memory writes and
logical operations on the contents of two 32 x 4 bit
static memory stacks (display and blinking) within the
LCD Display Decoder. The stack is arranged such that
COMM-0 thru COMM-3 (backplane) each equate to a column
and S0 thru S31 (segment) each define a row. Individual
memory cells intersect a COMM-n (where n is 0 to 3) and
Sn (where n is 0 to 31) which in turn map to a specific
segment of the LCD display. The LCD Display Decoder
operates as a quadruplexed 3- level biased driver, hence
the several voltages at VLC1 , 2 , and 3. Presence of a
logical "1" in the display RAM causes the driver to
excite the segment by increasing the RMS voltage between
the backplane and segment drives. Blinking RAM functions
in a similar manner except that the memory contents
determine whether the segment blinks or remains steady
state. Whenever a function is initiated, several hundred
bits of information are transferred to the LCD Display
Decoder. In turn, the memory contents are either written
directly with a nybble of data or logically manipulated
with a 4 bit operand contained within the command byte.
Provided the display is static (i.e. manual mode) and the
transfer complete, the Decoder performs all housekeeping
functions associated with maintaining the display while
the serial bus idles.
PHASE III is now underway to design a hardware inter a
that will buffer and convert relevant synchronous data~to
asynchronous (UART) for transfer to the serial port of an
IBM/compatible PC. Hardware will be included to program
or operate the scanner from the PC keyboard. Software is
currently in the development stage and will be written to
support a bi-directional interface with the PRO-2004/5/6.
LCD Display data will be sent along with a log and date-
time stamp. Long range projections include S-meter data,
event counter versus time, DTMF decoding, etc. The beta
release will have a rough core program to boot-up and
run, however the source code will be provided for the
adventurous programmers who want to carve their mark
within the PRO-2004/5/6 user community.
[EDITOR'S ROTE: HB-Technologies is using a PRO-2004 for
their developmental model, but fortunately anything done
by the PRO-2004 can also be done by the PRO-2005/6. In
case you technical types want to follow along closely
with the above discussion, I have listed various IC's
which were alluded to above. Refer to the below chart
and to your Service Manual/schematic to correlate Mr.
Bond's discussion with your scanner: /be]
LOGIC/CPU/DISPLAY CHIPS IN THE PRO- 2004/5/6
LCD Display Decoder
Random Access Memory
PLL Data Decoder
* * FEATURE PRESENTATION * *
AN EXTENDED DELAY FUNCTION
FOR MOST ALL SCANNERS
EUREKA, I have found it! An Extended Delay Function for
most any modern scanner! It is just as simple & easy to
fabricate as the one for the PRO-2004/5/6, MOD-29, page
156, in Vo 1-2 of my SCANNER MODIFICATION HANDBOOK.
Readers of that book will know from page 157 that the
alternate circuit for other scanners calls for a third
chip and plenty of extra wiring. Some folks had problems
with that design probably because of greater complexity
and it certainly wasn't readily installed in a handheld
scanner. Well, I didn’t see the forest for the trees
when Mark Persson submitted the design of MOD-29 for the
PRO-2004/5/6 and my way to make it compatible with other
scanners was not the best possible, though it does work.
Comes now virtually the same circuit as the one for the
PRO-2004/5/6 and in fact it is the same with two w g
changes from the diagram on pg-156 in Vol-2 of my boor.
The differences are for this new circuit are easily
described: refer to page 156 in Vol-2 of my book, and:
"THE WORLD SCANNER REPORT " (c) 1991; V1N9 - October, 1991; Page 4
At U-1, Pins 3, 4 & 5, remove Pin 5 from 3 & 4. Leave 3
i 4 connected, though. Lift the wire at U-1, Pin 2 and
reconnect it to the now empty U-1, Pin 5. Jumper U-1,
Pin 1 to the now empty U-1, Pin 2. THAT IS ALL THERE IS
TO IT, folks! Why I didn't see it before, I dunno; gross
* — - ignorance and sheer stupidity, maybe.
Let me emphasize that the PRO-2004/5/6 and maybe other
scanners still require the circuit shown on page 156 of
VoI-2 of my book. In cases where THAT circuit won't
serve the purpose, first delete the alternate circuit on
page 157 and use this month's circuit for most any other
scanner. If you prefer a picture to words, relax.... the
new circuit, MOD-29b, is given for you in Fig-5.
Now two versions of the same basic circuit can offer an
Adjustable Extended Delay for virtually all scanners.
For the sake of clarity, we'll refer to the version for
the PRO-2004/5/6 on page 156 of Vol-2 of my book as
HOD-29 ; the discontinued bulky circuit on page 157 for
other scanners will be MOD-29a . Its replacement in this
issue is now called MOD-29b .
So why would you want an Extended Delay Function? Think
about it from two angles: one obvious need is when the
speed of the scanner is boosted with a change of the
CPU's Clock Resonator. This resonator sets the timing of
all the scanner's functions, not only speed, but also
DELAY! Host scanners offer about a 2-sec delay but when
the speed is doubled as we seem to favor, DELAY is cut in
half. For a PRO-34 boosted from 8 ch/sec to 30, you may
is well forget having ANY delay. Reduced or no DELAY can
be a major drawback to serious scanning. Another point
of view involves unmodified stock scanners. With a mfgr-
provided DELAY function, you're limited to what's there
with hardly any control except maybe an ON/OFF feature.
Right off, I don't know of any stock scanners that offer
an adjustable DELAY function. But WHY should we be stuck
with the mfgr's meager handouts? There are times when
less than 2-seconds DELAY is good and other times when 5
or 10 seconds is better. Why not an Adjustable Extended
Delay? It can be done to most any scanner!
How Scanner Delay Works
The CPU of a scanner usually controls the DELAY function,
and there's not a heck of a lot of influence we can exert
on the little bugger. Fortunately, there has to be some
form of logic to tell the scanner when and when not to
run the DELAY function. That logic is similar in all
modern scanners and its source is the infamous NFM/AH
chip that we've discussed in several back issues so far
(V1N4, V1N7 & V1N8). You will recall that one of four or
five chips, all pretty much the same, is used in most
every scanner now. The NFM/AH chip has many functions,
two of which are to generate SQUELCH signals, one for the
/^receiver's audio section to silence static when nothing
is received and the other for the CPU. It's that special
SQUELCH signal for the CPU that captivates our interest.
This signal tells the CPU when it should SCAN or SEARCH
and when it should stop or lock up. It also activates
the stock DELAY function when selected. This is done as
a transmitter unkeys and the SQUELCH resets. The "reset"
action starts the CPU's DELAY countdown timer. Since
we're dealing with a timed function, any SCAN & SEARCH
speedups will decrease the scanner's stock DELAY time.
This logical SQUELCH signal has two states, ON and OFF,
usually 0 (low) and 5 or 8 volts (high). The SQ-Logic
signal originates in the NFM/AM chip and can be low (0-v)
when the SQUELCH is Set and 5 or 8 volts when the SQUELCH
Breaks; or vice-versa. This low/high logic is recognized
by the CPU's internal programming which enables it to
make "decisions" on when to resume SCAN or SEARCH and
when to initiate and timeout the DELAY function. Simple.
The only difficult part is that some NFM/AM chips
generate a low/high logic for SQ-Set and SQ-Break, where
other chips are high/low for SQ-Set and SQ-Break. To
make your job a little easier, Table 2 will identify for
various scanners the NFM/AM chip; the associated SQ-Logic
Pin #, and the type of logic. Depending on that logic,
you'll select either MOD-29 or MOD-29b for your scanner.
HOD-29 was originally developed exclusively for the
PRO-2004/5/6, where the SQ-Logic out of the NFM/AM chip
is low-SQ-Set and high-SQ-Break but that logic is
inverted to opposite logic before going to the CPU. In
other words, the PRO-2004/5/6' s CPU interprets a 0-v low
SQ signal to mean SQUELCH-Break and a 5v high signal as
SQUELCH-Set. Yet, the NFM/AM chip in the PRO-2004/5/6
works just the opposite but its logic is inverted by IC-3
before being sent to the CPU. This means that either
Extended Delay circuit can be used in the PRO-2004/5/6,
but since the easiest access point for installation of
the Extended Delay Board is between the CPU and the
Inverter, IC-3, we have to use MOD-29 at that point. You
could use my new MOD-29b if installed between the NFM/AM
chip and IC-3 but there's no sense in that because access
to that area is limited. THIS IS A CLUE, however, for
brand-x" scanners, some of which may also have inverters
in the SQ-Logic line. You may have a choice of either
circuit and where to install it. Keep this in mind later.
How To Extend A Scanner’s Delay Function
Easy! Remember that the NFM/AM chip generates the SQ-
Logic signal, so if we intercept that signal along the
way to the CPU and delay or postpone its change of state
when SQ resets, the CPU cannot initiate resumption of
SCAN or SEARCH until it senses the logic change. We
can’t do much about how the NFM/AM chip generates the
SQ-Logic but we can intercept that SQ-Logic and process
it to generate an artificial delay. Now it's a matter of
the proper circuit and where to intercept the SQ-Logic.
Where To Insert An Extended Delay And Which One?
First, let's identify the NFM/AM chips and their SQ-Logic
pins for a number of scanners so you will know what to
look for and which circuits to examine and may the Cosmic
Light help you if you don't have a Service Manual for
your scanner because I sure won't!
"THE WORLD SCANNER REPORT' (c) 1991; V1N9 - October, 1991; Page 5
TABLE 2: NFM/AM CHIPS &
SQUELCH LOGIC OUTPUT PINS FOR VARIOUS SCANNERS
TK- 1 0420
TK - 1 0420
TK- 1 0420
TK- 1 0420
TK- 1 0420
1 C- 101
1 C- 101
TK- 1 0420
TK- 1 0420
TK- 1 0420
• / •
SR- 1 5
R- 1 600
? = Unknown or not sure
* S/B = SQ-Set/SQ-Break (volts)
Using the above information for YOUR scanner, start at
the NFM/AM chip and its SQ-Logic pin, (in some scanners,
this is called the SCAN CONTROL function), and trace the
line to the CPU (if that's where it goes; some don't).
As you follow the trace, you will probably run into a
couple of resistors and capacitors along the way and
maybe a branch (Y) or two, but stay on the main trace to
the CPU and identify that pin of the CPU as the SQUELCH
or SCAN CONTROL input. Once you’re familiar with the
circuit, go back to the NFM/AM chip's SQ-Logic pin and
again work forward to the FIRST place where you can
intercept that SQ-Logic path. Such a spot might be a
resistor, or perhaps an exposed circuit trace or, if
you're lucky, a handy wire. This spot may be cut later
and the Extended Delay Board connected between the cuts.
First, measure the voltage of the logic levels at that
point. Rotate the SQUELCH back & forth to make it Set
and Break. If the low logic is between 0 - 1.7v and if
the high state is 4.2 - 5.5v, then one of my two Extended
Delay circuits will work. Now let's determine which one:
Again, measure the logic voltages at the chosen intercept
spot. If Squelch is SET (silence) and the spot measures
between 0 and 1.7-v, and if when the Squelch breaks
(noise), the spot measures between 4.2v and 5.5v, then
you'll need the circuit in this issue, MOD-29b. If
measurements at your chosen intercept are high (4 . 2-5 . 5v)
for SQ-Set and low (0-1. 7v) for SQ-Break, then you’ll
need MOD-29, page 156 in Vol-2 of my SCANNER MODIFICATION
HANDBOOK. I’m giving you this method of deciding because
your scanner may have a logic inverter between the NFM/AM
chip and the CPU like the PRO-2004/5/6. The specific
circuit of choice will be dependent on the logic of the
intercept spot you selected. It is impossible for me to
give explicit directions for all scanners because of the
variables discussed above. But if I teach you how to
determine for yourself — then mission accomplished!
Find a good spot to intercept the SQ-Logic signal, but
before you cut that path, make sure it's between the
NFM/AM chip and any branches or Y’s. After cutting the
path, the broken lead closest to the NFM/AM chip will be
the SQ-INPUT lead to the new Extended Delay Board. The
other broken lead will tie to the SQ-OUT and continue on
to the CPU or where ever it is supposed to go from there.
If all circuit tracing fails to disclose a prime lock_^n
to connect the EDB, you can always snip the SQ-Logic pin
of the NFM/AM chip and install the EDB between the cuts.
The main caution here is that the logic voltage must be
0-1. 7v, low and 4 . 2-5 . 5v , high. See IMPORTANT NOTE below.
IMPORTANT NOTE: there are caveats. MODs 29 and 29b are
designed for scanners where the CPU operates on +5 volts
and/or where the SQ-Logic is near 0 and 5 volt levels.
You should determine the operating voltage of the CPU
first before installing the EDB because if the CPU runs
on f 8 volts, you'll have to substitute U-1 and U-2 of the
EDB with 8v equivalents, probably the CMOS 4000 series.
I haven't done the research for this contingency so make
sure first. All scanner CPUs of which I am aware operate
from +5v but don’t take that to the bank.
Next you must measure the actual SQ-Logic voltage at the
selected intercept point for the EDB. If it’s more than
5.5v, you will either have to make a voltage divider/
reducer to drop that higher voltage down to +5 volts or
else find a place on the SQ-Logic line that has 5-volt
logic. I mention this because U-1 & U-2 of my EDBs are
rated at a max 5.5 v input/output and DC power. Also,
NFM/AM chips in the PRO-2004/5/6 and some other base
scanners happen to run from +8v which results in SQ- c
of about 0 and 8-v. Most scanners of this type will have
a voltage divider/reducer for the CPU somewhere near the
NFM/AM chip anyway, so maybe you can break the trace
after the voltage reduction point.
"1HE WORLD SCANNER REPORT " (c) 1991; V1N9 - October, 1991; Page 6
It is essential, however, that the EDB be inserted in the
SQ-Logic trace at a point between the NFM/AM chip and the
first branch or "Y". Squelch Logic sometimes has to
branch off to serve the needs of other circuits, too, so
the EDB must serve any branch paths in addition to the
CPU. If the SQ-Logic at the EDB insertion point is
greater than 5.5 volts, it will have to be reduced before
going into the EDB. This means then, that 5 volts will
exit the EDB which then could be too low for the circuit
ahead, so you'll have to look for the voltage divider/
reducer down the line and clip it out of circuit since
the EDB’s 5-v will be just right for those circuits
without further reduction. The very best thing you can
do where the SQ-Logic exceeds 5.5 volts is to trace that
circuit down and install the correct type of EDB at a
point after where the SQ-Logic is reduced to 5-volts.
About The MOD-29b Extended Delay Circuit
Here’s how MOD-29b works; first let's assume the Extended
Delay is OFF so that you either have no delay at all or
only the scanner's stock delay; in other words, NORMAL.
When S-1 of the EDB is open (off} , a high (+5v) is on
pins 12 & 13 of U-1; the output of which is inverted to a
low (0-v) at Pin 11. This low is sent to U-2, Pin 3
which deactivates U-2 and creates a high (+5v) at U-2,
Pin 4 which sends that high back to U-1, Pin 5. Assuming
that the SQUELCH is set, a low is coupled out of the
NFM/AM chip into Pins 9, 10, 1 & 2 of U-1. Since U-2 is
inactive, the effect at Pins 9 & 10 is not pertinent. A
low on Pins 1 & 2, however, is inverted to a high at U-1
’in 3 and then to Pin 4 of U-1 where a high already
exists at Pin 5. Highs at Pins 4 & 5 are inverted to a
low at Pin 6 which is then sent on to the CPU. Therefore
low-in equals low-out just as it should.
Now let's assume that the scanner's SQUELCH breaks with
an incoming signal. A SQ-Logic high is coupled into Pins
9, 10, 1 & 2 of U-1, and as before, since U-2 is
deselected, Pins 9 & 10 are of no consequence. The high
at Pins 1 & 2 is inverted to a low at Pin 3 of U-1 and
sent to Pin 4. A ’’permanent” high is on Pin 5 and with a
low on pin 4, the output of Pin 6 goes high, again as it
should. When the scanner's SQUELCH resets, the SQ-OUT
and the SQ-IN will always follow each other providing
normal SQUELCH and stock DELAY functions.
How close S-1 to activate the Extended Delay function.
This comes about by a low placed on U-1, Pins 12 & 13
which inverts to a high at Pin 11 and is sent to U-2, Pin
3 to activate U-2. If the SQUELCH is set, the SQ-ln and
SQ-Out will be low as normal. Now, when SQUELCH breaks
and SQ-ln goes high, the normal sequence as discussed
above happens again, except that the high on Pins 9 & 10
of U-1 is inverted to a low at U-1, Pin 8 where that low
goes to U-2, Pin 1 to prepare U-2 for action. Nothing
^1 se happens until the SQUELCH resets and SQ-ln goes low.
At the instant that SQ-ln goes low and which otherwise
would be sent on to the CPU as normal, a very interesting
effect is generated by U-2, a Retriggerable Monostable
Multivibrator. U-2, Pin 4 which is normally high, drops
low for a time that is determined by the values of C-1
and VR-1. C-1 is fixed, but VR-1 is the DELAY adjustment!
That low from U-2 Pin 4 is sent to U-1 Pin 5 which,
regardless of the value at Pin 4, makes Pin 6 remain HIGH
even though SQ-ln has gone low again! Pin 6 remains high
until the time set by VR-1 (0-12 sec) expires, at which
instant U-2 Pin 4 goes high again. In turn, this causes
U-1 Pin 6 go low to emulate SQUELCH reset, albeit
DELAYED! It's this elaborate process that artificially
creates a delayed SQUELCH Reset to the CPU, and in turn
delays the activation of the SCAN/SEARCH Resume function.
Another thing worth mention here is that the scanner's
stock/normal DELAY function will not be initiated until
the Extended Delay period has expired. Therefore, you
get two delays in series. If the Extended Delay is set
for 4-sec and the scanner's stock DELAY is 2-sec, then
you’ll have a total 6-sec delay if the normal DELAY is
set; if not, then 4-sec. This offers a 2-stage DELAY;
you can preset the stock DELAY function for some channels
and not for others which will have the effect of two
different delay times, depending, or set all DELAYS off!
Building. Installing & Operating the Extended Delay
Build the circuit on as small of a piece of perf-board as
possible, consistent with the space available in your
scanner. Don't get too luxurious in use of space because
you’ll want to install other mods later. If a handheld
scanner, you're going to have to carefully measure any
nooks and crannies and build the Extended Delay Board
(EDB) to suit what's available. This could mean that
you’ll have to build U-1 on one tiny board and U-2 on
another with a wiring harness between them to make things
fit! That's ok because layout and construction are not
critical. Just use very small and flexible hookup wires.
Install the switch and LED (if you want it) in a suitable
place on the exterior. VR-1 can be an ordinnary volume-
control type of potentiometer if you have the luxury of
mounting room; otherwise, a tiny trimmer potentiometer
can be rigidly mounted behind a hole drilled in the case
for access with a small screwdriver. Once you determine
a preference for an Extended Delay Time (mine is 4-sec),
it won’t be adjusted all that often, but it will be nice
to have the trimmer handy for when readjustment is
desired. I like the trimpot mounted behind a hole in the
case for occasional screwdriver adjustments. The right
kind of trimpot can be superglued to the inside of the
case for a convenient fit. Some trimpots can't be done
that way so beware; plan things out first.
There are three operable parts of the Extended Delay: the
LED for indicating whether it is On or Off; the switch to
turn the Extended Delay On or Off; and VR-1 by which to
preset the desired amount of Extended Delay, 0-12 sec.
The Extended Delay draws about 2-ma OFF and about 5-ma
ON, so current drain is not a major consideration.
PROBLEMS & DEBUGGIHG will be minimal or zilch if you
build the circuit properly and correctly install it in
the scanner's Squelch-Logic line. If you've done every-
”7HE WORLD SCANNER REPORT " (c) 1991; V1N9 - October, 1991; Page 7
thing perfectly, certain peculiarities might still arise.
For example, you've done the job and the scanner works
fine and the Extended Delay work but. .. .during the period
of the Delay, you may hear a static sound that sounds
like the receiver isn’t SQUELCHed. If you get this far
and this is the only problem, relax; you did everything
right and there’s no fault with the scanner or EDB. You
will just have a little more work to do to remedy THAT
difficulty. Understanding things is the first step.
Two SQUELCH-1 ike functions are generated by the NFM/AM
chip, one of which we’ve been working with above. The
other is called MUTE and is mostly an internal function.
MUTE is what performs the silencing of the receiver when
no signals come in. SQUELCH initiates the MUTE function
and sometimes does other things, too. Typically the
scanner’s CPU generates a MUTE signal based upon a SQ-Set
signal. During the period of the Extended Delay there is
no SQ-Set logic to the CPU so it "thinks" the scanner
should be UNMUTED and playing sound. The typical MUTE
signal from a CPU is 0v for MUTE and 5v for UNMUTE. The
0-v MUTE signal is usually applied to the vicinity of the
scanner's Volume Control which has the effect of shorting
out any undesired static and audio. This MUTE signal is
what silences the receiver. You can experiment with
using one of the signals from the EDB to serve as a MUTE
function during the period of the Extended Delay. The
signal at U-2 Pin 4 is normally high at 5v except during
the period of the Extended Delay where it drops to 0v .
U-2 Pin 13 (unused) provides an opposite logic to Pin 4;
it is normally low but rises to a high for the period of
the Extended Delay. Depending on what kind of MUTE logic
is used by your scanner, one of these two signals can be
pressed into service to MUTE the annoying static during
the Extended Delay period. I can’t offer much more help
on this because every scanner is different and different
techniques will be required for each scanner. But you
can get started with assessing and understanding the
scanner’s MUTE function and associated circuits. Just
remember, if you need my assistance, it will be gladly
given PROVIDED that you and I have a copy of the Service
Manual for your scanner. We can't work without it.
TEST your Extended Delay Circuit before installing it in
general accordance with instructions given in Vol-2, page
162. Use the logic (low/high) for the EDB that you built.
* * * PRESS RELEASE * * *
NEW SCANNER FREQUENCY RECORDS TOOL
DataFile, Inc. has announced the release of ProScan,
Version 1.0, a powerful, yet easy to use MS/PC-DOS
program designed for the scanner enthusiast desiring to
track frequencies and their users.
With ProScan, you can track up to 9,999 records by bank,
channel, frequency, name, location, class, type and call
sign. ProScan features include:
* user-selected display of records, by frequency,
channel, name, location or class
* Instant seek and select of individual records by
channel, frequency or name
* Print all or selected records by channel, frequency,
name, location or class
* Note pad with automatic date/time stamp
* Help screens
* Duplicate frequency check
* Automatic bank numbering
ProScan requires IBM or compatible, MS/PC-DOS version 2.0
or higher, 640k RAM, hard disk and works with IBM, Epson
and compatible printers. ProScan comes complete with
printed documentation. The regular price for ProScan is
$59.95. Until March 1st, 1992, ProScan is being offered
for a special introductory price of $39.95 (add $3.50 for
shipping in the US). To order ProScan, send check or
money order to DataFile, Inc, PO Box 20111, St. Louis, MO
63123. Please specify 5-1/4" or 3-1/2" disk. (Missouri
residents add $2.29 sales tax). IBM, PC-DOS & Epson are
trademarks of their respective owners.
BC-100XLT MEMORY EXPANSION UPDATE
A procedure is in V1N6 to liberate 100 more channels from
the BC-100XLT. Close, but no cigar. I was on the right
track but didn’t go far enough. More work is required.
Also needed are a small memory chip, switching transistor
& 4 resistors. The circuit board for the BC-100XLT is
the same as the one in the BC-200XLT, so the work left to
be done isn't extensive. Vacant solder pads are on the
8C-100XLT board for the parts. Order the parts f "m
Uniden because the transistor and memory chip wilt ^e
hard to find. Call UNIDEN PARTS DEPT; 9900 WEST POINT DR;
INDIANAPOLIS, IN 46250; (800) 428-5340 or (317) 842-1036
and order repair parts for the BC-200XLT as follows:
Component Ckt Symbol Part Number
Service Manual for the BC-200XLT
RZ021 (Unknown resistance va'
RZ021 <of R-250,
252 & 253.
in Serv. Manual
Service Manual to
locations where the above parts belong and install them
in your BC-100XLT accordingly. The step that I gave you
back in V1N6 is correct: remove & discard R-253; in its
place solder one end of a 47-k 1/4-watt resistor to the
original pad for R-253 that's closest to the CPU. Solder
the other end of the resistor to a nearby ground spot.
Install the above components in their proper locations
according to the BC-200XLT Service Manual, page 39. In
the process, remove & discard D-204 that's in the s
where R-222 goes. This will complete the steps to pin
100 more channels for your BC-100XLT. Sorry for any
inconvenience this slip may have caused. PS: Forget
adding 800 MHz to the BC-100XLT; just buy a BC-200XLT!
"THE WORLD SCANNER REPORT " (c) 1991; V1N9 - October, 1991; Page 8
FIGURE 5: EXTENDED DELAY FOR MOST SCANNERS EXCEPT PRO-2004/5/6 (MOD~29b)
A. This circuit for scanners with Squelch Logic that is
low for SQ-Set and high for SQ-Break and where low is
less than 1.7v and high is not greater than 5.5v. See
Note B if your Squelch Logic is 0 to 8v.
•-*. Use 100-k trimmer voltage divider/reducer if Squelch
>g ic exceeds 5.5v. Set trimmer so that middle lug of
trimmer equals 5.0v when SQ-High is present at top lug.
SEE TEXT. If 5v EDB output doesn't work because circuit
down line needs 8v, look for a voltage reducer/divider
and remove it.
C. Where SQ-Logic is 0 & 8v, you might consider using a
4011 Quad NAND and a 4538 Multivibrator . Pinouts of
these two chips differ from above so the circuit will
have to be changed accordingly. Just correlate each
function shown above with the new chips. Vcc for
■series chips will be 8-v, of course.
SG-L06IC GKCffTeR, THAhJ S-SV
r SQ- LO<r/C
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( /fDSUST 7Z>£PO#£ \
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Sq-'/M A-^OMe. /
"THE WORLD SCANNER REPORT " (c) 1991; V1N9 - October, 1991; Page 9
THE BELOj QUEST I OHS APE OPTIONAL BUT KILL HELP US HELP YOU!
Radio Interests? (Put YEARS OF EXPERIENCE in each block that applies)
VHF-UHF Amateur CB Shortwave Professional
Scanning? Radio? Radio? Listening? Radio?
-.it makes A models of your scanners & other radio equipment:
Describe your technical abilities & interests; use reverse as needed.
09/26/91 SUBSCRIPTION RATES i ORDER BLANK V1N9
USA RATES: (Canada tltt; Other Foreign +2l>-surf or Hit-Air)
BACK ISSUES OF THE NSR Check Items
1991 Single copies; your choice: 1 ea $ 4.00
1991 (1st 6-mos, Jan-June) 5 ea $15.00
CURRENT SUBSCRIPTIONS, with and without Back Issues (Bl)
1991 (2nd 6-mos; Jul-Dec, w/o Bl) 5 ea $15.00
1991 (1-yr; Jan-Dec, w/BI) 10 ea $25.00
1991-92 (1-yr; Jul-Jun, w/o Bl) 10 ea $25.00
1991-92 (1.5-yr, Jan-Jun w/BI) 15 ea $35.00
1991-93 (2-yr Jul-Jun, w/o Bl) 20 ea $45.00
1991-93 (2.5-yr, Jan-Jun w/BI) 25 ea $52.50
OTHER LITERATURE AVAILABLE
SCANNER MOD HNDBK, Vol-1: $17.95 ♦ $3.00 SSH »
SCANNER MOD HNDBK, Vol-2: $17.95 + $3.00 S&H *
♦(Canada $4 S&H ; Other Foreign $5 SBH; add extra for Air Mail)
HOBBY RADIO BUYER'S DIRECTORY (600+ listings) $14.95 ppd
HAKE mUIML WMLE 111 US FUNDS TO: COMKOHICS EHGIHEEH IHG
Enclose a 010 S.A.S.E. and one loose extra stamp if you want
hobby info & personal reply! Business inquiries exempt.
* * * THE SCANNER MOO HANDBOOK CORNER * * *
DISASSEMBLY & TEAR DOWR OF THE PRO-34 S PRO-37 : Gosh, I
guess it's about time the disassembly procedures for the
PRO-34 and the new PRO-37 were updated. Refer to the
Steps of Procedure in Vol-1 of the SMH, page 146, Step 8.
Wipe out that sentence; there's a better way: Follow the
GREER- YELLOW-BLACK wire bundle from the Volume Control to
the brown plug; pull the wire bundle UP so that the brown
plug disconnects; push the wire bundle over the top end
of the scanner. Follow the RED-WHITE- BLACK wire bundle
from the SQUELCH control to the white plug; pull the wire
bundle UP so that the white plug disconnects; push the
wire bundle over the top end of the scanner. It's not
necessary to remove the VOLUME and SQUELCH controls; just
unplug their wire bundles! The rest of the
Disassembly/Reassembly instructions for the PRO-34 are
pertinent and applicable; most likely to the PRO-37, too.
SPOT-WELDED SHIELD COVER? After getting a few reports
from around the country about some PRO-34's with a welded
cover between the two PCB's, I warned of this possibility
in Step 10, page 146. It's examined again in Vol-2 of
the SMH, HINT-3 pg 16 by a well-meaning hobbyist who
figured out how to "break the welds” on that shield
cover, actually a metal frame! Unfortunately for HIM, the
metal frame between the two PC8's is always held in place
by three tiny screws, one each in the upper corners of
the frame and one in the middle by the battery. I guess
lots of people didn't look close because sure enough, the
flat shield is spotwelded to the sides of the frame. But
who cares? The frame/shield assembly lifts out after the
three tiny screws that hold it down are removed! THERE
IS NEVER A NEED TO BREAK THE WELDS! Remove the three
screws instead and they really are there. By the way,
Catch-22 about those screws is that one is shorter than
the other two. The shortest screw goes in the end hole
by the battery. If you put a long one in there, it will
bulge the keyboard panel on the front of the radio.
PRO- 2(8(84/5/6 POSSIBLE FAILURE MODE
A real "dog" of a PRO-2004 came through my shop recently.
The owner said that the problem had sporadically showed
up since the scanner was brand new but it had finally
crapped out for good. The symptom was obvious: turn j
scanner On and the Display lit up with the familiar biue
glow but nothing else happened; no scan, no numbers, etc.
Power supply voltages were ok so my initial diagnosis was
"faulty solder joints" or bad connections on the Logic/
CPU Board; a common problem among some PRO-2004' s. Fifty
to a hundred resoldered joints later and no remedy, I
looked deeper. It took a while but I finally found the
problem and learned something for my efforts.
There is a function in the PRO-2004/5/6 CPU called HOLD.
It's not anything to interest the average hobbyist and is
not discussed in the Owner’s Manual nor even the Service
Manual. If you’re not initiated, the schematic doesn't
even offer much of a clue on the purpose of HOLD. But
it’s a big one, turns out; to let the CPU know when to go
to "sleep" (power off) and "wake up” (power on). Without
getting too technical on you, there is a transistor that
senses when the Memory Retention Battery is active and
which can happen ONLY when power is OFF. When the
scanner is ON, the transistor sends a low (0-v) to the
CPU and makes it's current draining memory circuits "wake
up”. A high (5-v) tells the CPU when the scanner is OFF,
so that it can shut down current drain and go to "sleep".
This is why the Memory Battery lasts for months; only a
few microamps are required to keep memory fresh and r'Hy
for action when the scanner is turned on.
In the above problem, I found this transistor to be blown
out for no apparent reason. Replacement with a common
NPN 2N3904 restored the scanner to proper operation. It's
Q-30 in the PRO-2004, and Q-29 in the PRO-2005/6.
CHECK YOUR MAIL LABEL : IF YOUR EXPIRE DATE SAYS "Rov 91“
REXT ISSUE WILL BE YOUR LAST : REREW EARLY FOR 1992!
"THE WORLD SCANNER REPORT" (c) 1991; V1N9 - October, 1991; Page 10
COMMTRON I CS ENGINEERING
"THE WORLD SCANNER REPORT"
PO BOX 262478
SAN DIEGO, CA 92196-2478
IN THIS ISSUE FIRST CLASS HAIL
+ Sony ICF-2010 Failure 4 Repair
+ Efforts to develop a PRO-20M/5/6 PC Inyerface
* Extended Delay function for All Scanners
+ NFM/AM Chips for More Scanners
+ New Scanner Frequency Records Tool
+ BC-100XLT Memory Expansion Update
+ PRO-34/37 Disassembly Procedure Update
+ PRO-34 Spotwelded Shields; Myth Debunked
4 PRO-2004/5/6 Failure 6 Repair
t SUBSCRIPTION ABOUT TO EXPIRE? RENEt EARLY!